Preparation of winter oil from cottonseed oil



Patented June 25,. 1940 PREPARATION OF WINTER OIL FROM COTTONSEED OILEdayw. Eckey,.Wyomlng, and Robert G.Folzenlogen, Lockland,

- Ohio,

assignors to The Procter & Gamble Company, Cincinnati, Ohio,

a corporation of Ohio No Drawing. Application July 6, 1939. Serial No.283,062 g Claims. (01. zso-42s) This invention relates to an improvedprocess for preparation of winter'oil from cottonseed oil.

Its principal object is to prepare an oil.suit

able for a salad oil for table use, that is, one which will not becomecloudydue to deposition of stearine even at the lowest temperaturesordinarily occurring in homes.

A further object is to shorten the time heretofore consumed in thecommercial process of cooling cottonseed oil and the subsequentcrystallization of the stearlne from same, with a correspondingreduction in the space required forthe operation.

Our process consists essentially in supercooling the oil by coolingit sorapidly from a temperature at which the oil is perfectly limpid to atemperature a few degrees below the temperatureat which the bulk of thestearine is to be crystallized out that the oil acquires a supercooledcondition without separation of stearine, and then allowing the stearine,to crystallize spontaneously from the oil'without further refrigerationbut allowing the temperature of same to rise slightly due to the heatevolved by the crystallization of the stearine, after which the stearineis separated leaving an olein having the desired properties for use as asalad oil.

The oil ordinarily used in this process is what is commonly known as"summer yellow" cottonseed oil, although bleached oils can also be usedif desired. This is produced from ordinary crude cottonseed oil by thewell known alkali refining treatment. It is important that the oil befree from moistureand suspended matter or dissolved soap, etc.; if it isperfectly clear at a temperature of 70 F., it will be satisfactory inthese respects.

Ordinary refined cottonseed oil (summer yellow oil) consists essentiallyof a. mixture of glycerides of various higher fatty acids, some of whichglycerides are liquid at ordinary temperatures and others are solid. Themixture, however, is a clear liquid at ordinary room temperatures. Atlow temperatures,- however, some of the solid constituents crystallizeout forming what is known as'-stearine and leaving a liquid portionknown as olein."

' contains little, if any true stearic acidbut consists mainly ofglycerides containing palmitic acid. vTemperatures belowabout F.generally show some separation of stearine but the bulk of the stearinedoes notseparate until -the tem-' The so-called stearine crystallizingtemperature for a considerable time before crystallization sets in toany great extent. This is due to supercooling to which the oil is easilysubject. The olein constitutes the ordinary winter oil of commerce and,for commercial purposes, it is required to pass the" cold test asdescribed in the Rules of the National Cottonseed Products Association,wherein a four-ounce bottle of the oil must stand immersion in meltingice for five hours without becoming cloudy.

. Ordinary winteroils will develop cloudiness if held suiiiciently longin this test, but not in the livehour period prescribed. A further smallquantity of stearine can "be separated from such winter oils bysubjecting them to a second crystallization at a lower temperature thanthat ofthe first crystallization, and the oil willthen have aconsiderably longer cold test" and it will stand a correspondinglylower'temperature without clouding.

In making winter oil heretofore, the necessary refrigeration has usuallybeen applied over. substantially the whole period during whichcrystallization is actually taking place. The coolingTias beenaccomplished, in one system, by first filling a large tank with the oilat a temperature-of- -'l0 F. to 90 F., at which temperature it is cleargenerally no agitation is used. Refrigeration inboth procedures iscontinued until .cryst'alliza-' tion of stearine has progressed to thedesired extent. In either case the oil remains substantially stationary,so the transfer of heat is slow,

and these chilling processes on thelarge masses of oil commonly usedusually require about thirty hours or more with the brine coil system,

and several days with the refrigerated air system,.

to chill the oil from -90? F. to the crystallization temperature and tocontinue the refrigera tion until the crystallization of stearine issubstantially complete. The temperature at whichmost of the-stearinecrystallizes from summer cottonseed oil is usually about 42 to 45 F.,although the stearine usually begins to crystallize .at temperaturesslightly below -60 F. The

crystallized stearine is then separated, usually by filtration in afilter press followed by blowing with air, thus obtaining the olein foruse as salad oil.

Itf'is ipossible to recover commercially from average summer cottonseedOH in the above described manner, eighty-five per cent to eightyeightper cent of marketable winter oil with twelve per cent to fifteen percent of marketable stearine having a titer test of 44 to 45 C., but

. tained more than a few degrees below that of the oil, the effect is toovercool those portions of the.

oil nearest to the refrigerating medium so that they may actually freezesolid without allowing the stearine to separate in grains from theolein; in other cases, the result may be a rapid crystallization .in theform of fine particles of stearine which cannot be filtered out.Agitation throughout the cooling and crystallizing period in largemasses of oil likewise prevents crystallization of stearine in the formof large crystals which can be filtered.

In our process we cool the oil very rapidly,-

while it is moving over the refrigerating surface, so that asupercooling effect is obtained.

The entire cooling takes place before there is any separation ofstearine, or at the most only a very slight separation. We accomplishthis preferably by passingthe dry oil at a temperature' of at least 60F., but warm enough to be clear and limpid, continuously into andthrough a suitable heat exchanger supplied with a cooling medium such ascold brine, the temperatures and rates of fiow of the two liquids beingso regulated that the oil issues from the heat exchanger with thedesired temperature. The oil should preferably be well agitated. duringits passage through the heat exchanger in order to secure uniformcooling and to prevent excessive local cooling of any portion of theoil. The cooling operation may thus be made continuous, and the oil maybe completely cooled without exposure to the refrigerating surface form'ore than a minute or two, as only asmall amount of oil is in contactwith the refrigerating surface at any one time. In. any event thecooling operation should not ordinarily extend over 30 minutes in orderto assure the desired super--- cooling-effect. The temperature to whichthe oil is cooled should be about 2- to F. below the temperature atwhich the'stearine will separate' in large quantities or the temperatureto which the oil will subsequently rise due to the heat ofcrystallization of the stearine. Th s latter temperature is referred toherein as the "temperature of graining. In this way all the re-'frigeration required for crystallizing the stearine in our process isapplied to the oil before crystallizing actually begins. The besttemperature to which the oil should be cooled is usually about 41 to 44,depending on the nature of the oil and the amount of stearine which itcontains, but not-below 40 F., and can. be: readily determined in eachcase by a preliminary laboratory test or by observation of previousbatches of the same oil. Care must be taken not to supercoolthe oil to'an excessively low temperature,- as this may cause the subsequentseparation of stearine to occur too rapidly and in a form diflicult tofilter.

After cooling, the oil is accumulated in a suitable tank where it isheld without further reduction of temperature, and with protectionagainst changes of temperature due to other causes than the natural heatof crystallization, until the desired crystallization of stearine oc-'curs, which requires from ten to twenty hours for completion. During.the first few hours of this stage the oil is gently agitated, (usuallyabout two-to six hours, or until crystallization is well under way),after which it is found best to allow the oil to rest without furtheragitation until the crystallization of stearine is completed. Duringthis stage the temperature will riseseveral degrees, sometimes as muchas 5 F., due to the heat of crystallization. The separation of stearineis considered complete when no further rise of temperature takes place,and then the oil is ready for separating the stearine by filtration orcentrifuging, etc.

In practice we find it best to maintain the atmosphere surrounding thetanks of oil for'crystallizing at a temperature either the same as thatof the oil or one or two degrees below the temperature of the oil, inorder to assure that no access of heat to the oil takes 'place fromoutside sources during the crystallization; if this were not done, andif the surrounding air had a higher temperature than the oil, it wouldmake necessary further cooling of the oil to offset the heatingefl'ectof the higher surrounding temperature during the subsequentcrystallization. It is not intended however to impart any additionalrefrigeration to the oil at this stage. 4

We prefer to. agitate the oil during the first portion of thecrystallization stage with a gentle current of air or other gas,avoiding in all cases strong agitation, This is continued only untilabout the time when crystallization of stearine has produced noticeableturbidity, after which agitation is stopped. We find that if the oil hasbeencooled to as low as 41 F. about one hour of agitation is enough; ifthe oil has been cooled to 43"; we agitate about four hours; and if theoil has been cooled to about 44 to 45 we agitate as much as eight or tenhours. In any event the oil then remains quiet throughout the remainderof the crystallization period. Practically no temperature rise occursduring the period ofagitation when conducted as here specified, butafter this is stopped and rapid crystallization sets in the temperaturegradually rises and may go up as much as 5 F- The time required forcrystallization can be considerably reduced by the process of seedingthe super-cooled oil by adding asmall amount,-

such as about two to five per cent for example,

of the crystallized oil from a previous batch, or.

an equivalent quantity of crystallized stearine from a previous batch,which would amount to,

not over one per cent of. the stearine. This should be added to the oilimmediately after cooling. I Q

The agitation is then limited to about one hour and the separation ofstearine, is completed in a much shorter time than otherwise. oftentimesthe time is as short as seven hours. I

The advantages of our new procedure are mainly the greatly reduced timefor completion of the operation, the correspondingly reduced spacerequired for production of a given amount of winteroil, and the reducedloss of refrigeration due to the greatly reduced time of chilling, It isnovel, as far as we are aware, to find that cottonture below the finalcrystallizing point of the oil without separating stearine, and thenwithout further refrigeration to have the stearine crystallizespontaneously in a form which will permit a satisfactory rate offiltering. This rapid chilling is contrary to all previous experienceand theories for the production of winter oil.

-Having thus described our invention, claim and desire to secure byLetters Patent is:

l. A process for separating stearine from refined cottonseed oil whichcomprises cooling the oil from a temperature above-its grainingtemperature at which it is limpid to a temperature at least 2 F. belowits temperature of graining but not below 40 F., the rate of coolingbeing sufiiciently rapid to avoid any substantial graining out ofstearine during said cooling, then protecting the oil from anysubstantial change of temperature due to other causes than the naturalheat of crystallization while stearinecrystallizes from the oil, andseparating the grained stearine from the olein.

2. A process for separating stearine from'refined summer cottonseed oilwhich comprises cooling the dry oil while it is in motion, from atemperature above its graining temperature at' which it is limpid to atemperature at least 2 F. below its temperature of graining but notbelow 40 F., the rate of cooling being sufiiciently rapid to avoid anysubstantial graining out of stearine during said cooling, gentlyagitating the oil until substantial crystallization begins, protectingthe ,oil from any substantial change of temperature due to other causesthan the natural heat of crystallization until crystallizationsubstantially ceases, and separating the grained stearine from theolein.

'3. A process for separating stearine from refined summer cottonseed oilwhich comprises cooling the dry oil while it is in motion, from atemperature above its graining temperature at which it is limpid to atemperature at least 2 F.

below its temperature of graining but. not. below whatwe- 40 E, therate'o! cooling being sufficlently rapid to avoid any substantialgraining out of stearine during said cooling, then adding to the cooledoil grained cottonseed stearine in solid form in an amount not exceedingone percent of the oil,

gently agitating the oil until substantial crystallization begins,protecting the oil from any substantial change of temperature due toother causes than the natural heat of crystallization untilcrystallization substantially ceases, and separating the grainedstearine from the olein.

4. A process for separating stearine from refined summer cottonseed oilwhich comprises cooling the dry oil while it is in motion, from atemperature at which it is limpid, but at least F., to a temperature atleast 2 F. belowits temperature of graining, but not below 40 F., withina period not exceeding twenty minutes, the rate of cooling beingsufliciently rapid to avoid any substantial graining out of stearineduring the said cooling, gently agitating the oil until substantialcrystallization begins, protecting the oil from any substantial changeof temperature due to other causes than the natural heat ofcrystallization until crystallization substantially ceases, andseparating the grained stearine from the olein.

5. A process for obtaining from refined summer cottonseed oil an oleinsuitable for use as a salad I oil, which comprises supercooling the oilbycontinuously cooling a moving stream of the dry oil from a temperatureat which it is limpid and above its graining temperature to atemperature from 2 to 5 F. below its graining temperature, the

rate of cooling being sufficiently rapid to avoid any substantialgraining out of stearine during said cooling, gently agitating the oiluntil substantial crystallization begins, protecting the oil from anysubstantial change of temperature due to other causes than the naturalheat of crystallization until crystallization substantially ceases, and

filtering the grained stearine from the olein,

EDDY w. ECKEY. ROBERT a. r'onzsnnoonn.

